Engine exhaust system



Dm L W7@ M. @OERMA ENGINE EXHAUST SYSTEM 2 Sheets-Sheet 1 Filed July lo, 1968 DML L W7@ M. J. @@ERMA ENGINE EXHAUST SYSTEM .2 Sheets-Sheet 2 Filed July 1.9, 1968 United States Patent Oiitice 3,543,509 Patented Dec. l, 1970 3,543,509 ENGINE EXHAUST SYSTEM Michael J. Boerma, Waukegan, Ill., assignor to Outboard Marine Corporation, Waukegan, Ill., a corporation of Delaware Filed July 19, 1968, Ser. No. 746,079 Int. Cl. F01n 7/10 U.S. Cl. 60-29 10 Claims ABSTRACT OF THE DISCLOSURE Disclosed herein is a marine propulsion device provided with an exhaust gas receiver. In one embodiment the receiver is in the form of a housing having inner and outer communicating chambers with the inner chamber located over the exhaust ports for the cylinders and the outer chamber communicating at its lower end with an exhaust gas passage which extends through the lower unit of the marine propulsion device. The back pressure at the exhaust ports or resistance to ow is equalized by providing ilow paths of equal distance for all the cylinders between the exhaust ports and the outer chamber. In a further embodiment, a deector plate located in the exhaust receiver restricts and impedes exhaust gas flow from the two cylinders closest to the exhaust tube to increase back pressure at these cylinders to the level of the cylinder farthest from the exhaust tube so that all cylinders contribute equally to the power output at idle and above idle speeds, thus facilitating carburetor idle adjustment.

BACKGROUND OF INVENTION In internal combustion engines which have a plurality of cylinders, the back pressure at the exhaust port of the cylinder closest to the exahust tube is generally lower than the back pressure in the exhaust system adjacent the other cylinders because of the cylinders proximity to the exhaust tube outlet. Thus, the cylinder closest to the exhaust tube is the predominant cylinder and contributes more power than the other cylinders. This causes the engine to idle lunevently and makes carburetor idle adjustment diflcult.

SUMMARY OF INVENTION The invention provides an exhaust receiver for a marine propulsion unit which equalizes the back pressure adjacent the exhaust ports of each of the cylinders to afford uniform power output for each cylinder thereby minimizing power losses and providing a smooth idle operation which facilitates carburetor idle adjustment.

In one embodiment of the invention the back pressure at the exhaust ports of all the cylinders is at least partially equalized by providing ilow paths of equal length from each exhaust port to the outer chamber of a common exhaust receiver, which chamber is connected at its lower end to an exhaust gas passage.

In a further embodiment of the invention the back pressure at the exhaust ports in a three cylinder engine is equalized by increasing the back pressure of the two cylinders closest to the exhaust gas passage to the level of back pressure at the other cylinder by wall means in the form of a deilector plate which includes baffle portions, which is located in the exhaust gas ow paths of the cylinders closest to the exhaust tube, and which decreases the size of the flow passages from these cylinders to the exhaust gas passage.

Further objects and advantages of the invention will become apparent from the following description and accompanying drawings.

DRAWINGS FIG. l is a schematic front elevational view partially broken away and in fragmentary section of a marine propulsion unit embodying the exhaust receiver of the invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1.

FIG. 3 is a side elevational view in fragmentary section with portions broken away of the marine propulsion unit shown in FIG. 4.

FIG. 4 is an enlarged fragmentary sectional view of a marine propulsion unit with a .further embodiment of the invention.

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4.

FIG. 6 is an enlarged perspective view of the deector plate shown in FIG. 4.

DETAILED DESCRIPTION In the drawings, FIG. 1 shows a marine propulsion unit which is generally designated 10 and which includes a powerhead or engine 11 with an engine block 12 having rst, second and third horizontally disposed cylinders 14, 16 and 18. Each of the cylinders 14, 16, 18 is provided with an exhaust port respectively 17, 19 and 20 in the form of three openings in the engine block 12.

In accordance with the invention means are provided defining an exhaust receiver 21, the exhaust receiver including means to at least partially equalize back pressure for all the cylinders. In the construction shown in FIGS. 1 and 2, the means is in the form of a housing 22 which extends the full length of the engine block 12 (FIGS. 1 and 3) and which communicates with the exhaust ports 17, 19, 20 of the cylinders. The housing 22 is secured to the engine block 12 by bolts 21A extending through outturned flanges 23. The housing 22 includes an elongated inner chamber 24 and an outer chamber 26.

Means are provided for separating the inner and outer chambers and providing exhaust How passages from the inner chamber 24 to the outer chamber 26. In the disclosed construction the means are in the form of a partition 28 (FIGS. 1 and 2) which connects housing side walls 27 and 29 and which is spaced between the upper wall portion 30 and lower or intermediate wall portion 32 to provide two openings or passages 34 and 36 through which the exhaust gases contained in chamber 24 flow into chamber 26. The outer chamber 26 communicates with an exhaust gas passage 38 which extends through the lower unit 40. The inner and outer chamber 24, 26, together with the openings 34 and 36 provide tlow paths of equal distance from the exhaust ports 17, 19, 20 to the outer chamber 26, thus tending to equalize or balance the back pressure at the exhaust ports of all the cylinders.

More specifically, the shortest distance from the exhaust ports of each cylinder to the: outer chamber 26 are equal in length. The distance from the exhaust port 17 to opening 36 is equal to the distance from the exhaust port 19 to either opening 34 or 36. The distance from the exhaust port 20 to the opening 34 is equal to the distances from ports 17 and 19 to opening 36. The equal distances tend to provide equal back pressures at each of the exhaust ports which promotes even power output and smooth idle operation which, in turn, facilitates carburetor idle adjustment.

Referring to FIGS. 4 and 5, a further` embodiment of the invention is disclosed in which the means defining an exhaust receiver is in the form of a housing 50 having first and second opposed spaced walls 52, 54 (FIG. 5) interconnected by a third wall 56. The walls 52, 54, 56 define an elongated open channel 58 which extends the full length of the powerhead 12 and is open toward the powerhead for communication with the exhaust ports 60, 62, 64 respectively of cylinders 66, 68, 70.

As shown in FIG. 4, the walls 52, 54, 56 taper outwardly and downwardly and the channel 58 progressively increases in volume as the channel extends from the upper cylinders 66 to the lower cylinder 70 to accommodate the additional exhaust gases furnished by the lower cylinders 68, 70.

In the embodiment disclosed in FIGS. 4 and 5, the means provided to equalize back pressure at the exhaust ports on all three cylinders comprises wall means in the form of a generally rectangular deector plate 72 which is located in channel 58, which has baille portions 74 and 76, and which impedes exhaust gas flow from the lower cylinders 68 and 70 into the channel 58 to equalize the back pressures at these cylinders with the back pressure at the upper cylinder 66.

More specifically, the deliector plate 72 extends from adjacent the exhaust port 60 of the cylinder 66 to the bal-lle portion 76 which is located in the approximate center of the exhaust port 64 of the cylinder 70. The defiector plate 72 includes a generally rectangular opening 78 located at the exhaust port 62 of the cylinder 68. The opening 78 provides a flow passage with smaller dimensions than the unimpeded flow passage 79 for exhaust port 60. The deilector plate 72 and baffle portion 76 provide a passage 81 from exhaust port 64 to channel 58 which has smaller dimensions than the passage 79.

The deflector plate has two inturned flanges 80 and 82 which extend inwardly into the channel 58 and which are in abutting engagement with the walls 52 and 54 to provide a pressure t for securing the deflector plate in its desired position. The deflector plate 72 also is provided with two alignment tabs 84 and 86 for locating the plate 72 relative to the engine block 12 and maintain the deflector plate at the appropriate position.

The back pressure at cylinder 66 is normally higher than the back pressures at the two lower cylinders because of the proximity of the lower cylinders 68, 70 to the exhaust outlet. The restriction afforded to the exhaust flow at the two lower cylinders 68, 70 as a result of the flow impedance caused by the opening 78 and the baie portion 74 and the restricted passage 81 increases the back pressures at the exhaust ports of the cylinders 68 and 70 to approximately the value of the upper cylinder 66. Thus, all three cylinders operate at approximately the same power level, providing smooth idle operation which facilitates adjustment of the carburetor or carburetors for idle operations.

Although the drawings show a three cylinder engine embodying the exhaust receiver of the invention, the principles of the invention can be utilized with engines having various numbers of cylinders. The desired balance of impedance to exhaust flow to obtain equal power levels of all cylinders at idle can be achieved either by equalizing exhaust ow paths to a common outer exhaust receiver or by restricting exhaust fiow from the cylinder or cylinders closest to the exhaust passage or tube by selection of appropriate openings and appropriate size baffle portions in the defiector plate. Ideally, the maximum advantage of the invention is achieved if the flow impedance for all the cylinders is balanced and causes equal power output of all cylinders. However, in practice at least some of the advantages of the invention will be obtained if the flow impedances are not in exact balance and the impedance provided for the lower cylinders, i.e., the closest to the exhaust passage, is approximately the same as the iiow impedance of the upper cylinders.

Various of the features of the invention are set forth in the following claims.

I claim:

1. An outboard motor comprising a lower unit having an exhaust gas discharge passage, and an engine located above said lower unit and including an engine block having at least vertically aligned upper and lower cylinders each having an exhaust port, said engine also including an exhaust gas receiver communicating with said exhaust ports and, adjacent the lower end thereof, with said exhaust gas passage, said exhaust gas receiver including wall means for controlling exhaust gas flow to reduce back pressure difference between said cylinders during operation.

2. An outboard motor in acocrdance with claim 1 wherein said receiver has a cross-sectional area which is available for exhaust gas flow and which increases from the upper end of said receiver to the lower end of said receiver.

3. An outboard motor in accordance with claim 1 wherein said exhaust gas flow controlling means includes means restricting the cross-sectional area available for ow from at least one of said cylinders.

4. An outboard motor in accordance with claim 1 wherein said ow restricting means comprises a deector partially blocking exhaust gas ow from said exhaust port of said lower cyilnder, whereby exhaust flow from said lower cylinder is impeded as compared to exhaust ow from said upper cylinder.

5. An outboard motor comprising a lower unit having an exhaust gas discharge passage, and an engine located above said lower unit and including an engine block having upper, lower and intermediate vertically aligned cylinders each having an exhaust port, said engine also including an exhaust receiver communicating with said exhaust ports and with said exhaust gas passage, said exhaust gas receiver including a deflector extending transversely across said lower and intermediate ports to partially block said lower and intermediate ports by reducing the cross-sectional area available for exhaust gas flow.

6. An outboard motor in accordance with claim 5 wherein said receiver communicates at the lower end thereof with said exhaust discharge passage and wherein said receiver has a cross-sectional area which is available for exhaust gas ow and which increases from the upper end thereof to the lower end thereof.

7. An outboard motor in accordance with claim 1 wherein said exhaust receiver comprises walls defining a commoninner chamber in communication with said cylinder exhaust ports, an outer chamber in communication with said exhaust discharge passage, and means for separating said inner and outer chambers and providing at least one ow passage between said chambers, said ow passage being located relative to said exhaust ports so that the shortest distances from at least two of said exhaust ports to said outer chamber through said flow passage is substantially equal.

8. A11 outboard motor in accordance with claim 7 wherein said receiver walls include two opposed side walls and upper and lower wall portions, and said means for separating said inner and outer chambers comprises a partition connecting said side walls, said partition having upper and lower ends, said upper end being spaced from said upper wall portion and said lower end being spaced from said lower wall portion to provide flow passages between said inner and outer chambers.

9. An outboard motor in accordance with claim 8 wherein said engine has first, second and third cylinders having rst, second and third exhaust ports, and said partition defines rst and second ow passages, said rst flow passage being located between and spaced from said rst and second exhaust ports and said second ow passage being located between and spaced from said second and third exhaust ports.

10. The combination of an engine block with at least two cylinders located with their respective axes in spaced parallel relation t0 one another substantially in one plane, each of said cylinders having an exhaust port, said engine also including an exhaust gas discharge passage extending from adjacent one of said cylinders in the direction of said one plane and at a substantial angle to said axes, said combination further including an exhaust receiver communicating with said exhaust port and with said ex haust gas passage, said exhaust gas receiver including a deector extending transversely across said exhaust port 6 of said one cylinder to partially block said port of said one cylinder by reducing the cross-sectional area available for ow from said one cylinder to equalize back pressure on said cylinders during operation.

References Cited UNITED STATES PATENTS 939,844 11/1909 Lehmann 60--29 1,760,553 5/1930 Hewitt 60-29 1,868,355 7/1932 Goldberg 60-29 2,899,797 8/1959 Birmann".` 60-32 3,091,078 5/1963 Dworak 60-29 DOUGLAS HART, Primary Examiner U.S. C1. X.R. 

